When it comes to the phrase "turn in", there are numerous synonyms that can be used to convey the same meaning. For example, you can use words such as "submit", "hand in", "give in", or "present". These words all convey the idea that someone is giving someone else something that is expected of them, like homework or a report. Other synonyms for "turn in" include "surrender", "deliver", "offer up", and "yield". In some cases, the specific context may determine the best synonym to use, but regardless of which word you choose, the meaning should be clear: someone is transferring something that is expected or required of them.